This invention relates to a liquid distributing device for use in an automatic analyzing apparatus, for delivering a given amount of a liquid such as a sample liquid from a sample cup into a reaction vessel comprising a probe to be immersed into the sample liqid contained in the sample cup, pumping means such as a syringe connected to said probe for sucking and discharging a given amount of the sample liquid through said probe and means for driving said syringe.
In automatic analyzing apparatuses, various distributing devices are used to deliver various kinds of liquid such as samples, reagents and diluents by means of one probe. Such distributing devices perform a sucking operation even if a liquid level of the liquid contained in a vessel descends below a tip of a probe and thus air is sucked in the probe. Therefore, the amount of the liquid sucked in the probe is smaller than a given amount to be delivered. This results in that the predetermined amount of the liquid could not be delivered and erroneous measurement might be introduced. In order to avoid the above mentioned drawback, it has been proposed to detect a liquid level of the liquid during the aspiration. This can be effected by providing a photoelectric detecting means having an elongated detecting region extending in an axial direction of the vessel, because the liquid level descends in accordance with the aspiration. Therefore, the photoelectric detecting means is liable to be large in size and complicated in construction. It has also been proposed to descend the probe in accordance with the progress of aspiration. However, in such a case, a very complicated probe driving mechanism must be provided.